MXPA00011287A - Encapsulated breaker slurry compositions and methods of use - Google Patents

Abstract

An encapsulated breaker slurry composition for reducing the viscosity of a fracturing fluid. The slurry has a flashpoint above 93°C, and the liquid of the slurry does not facilitate release of the breaker from the coating. Methods of using the slurry composition are also described.

Description

COMPOSITIONS IN LIQUID PASTE OF REDUCERS OR FRACTIONATORS OF IA VISCOSITY, ENCAPSULATED, AND METHODS OF USE • FIELD OF THE INVENTION This invention relates to encapsulated viscosity fractionators. More specifically, this invention relates to liquid pastes of encapsulated fractionators. 10 • BACKGROUND OF THE INVENTION Hydraulic fracturing of underground oil formations is a good technique known to increase the permeability of underground formations. In this technique, a viscous fluid ("fracturing fluid", commonly an aqueous fracturing fluid, more commonly guar) is introduced to the walls In the interior of the well, pressure is applied to induce fracture, and support materials in the fluid (most commonly sand) keep the fractures in an open state. Then the viscous fluid must be removed and the oil collection of the underground formation as well REF. : 124878 open. To facilitate the rapid removal of the fracturing fluid, chemicals are used to reduce or "fractionate" the viscosity of the • fracturing fluid; these chemicals (most commonly oxidizers, and in particular persulfates) are known as fractions. "The chemical reaction of the fractionator with the fracturing fluid is undesirable before the end of the operation. fracture. Therefore, it is advantageous to encapsulate or coat the particles with a polymer to retard the release of the fractionator, and hence retard fractionation of the viscosity of the fracturing fluid. In the art many materials have been used to encapsulate fractionators to fracture fluids. For example, U.S. Patent No. 4,506,734 (Nolte) describes a • fractionator inside a coating Glass or ceramic, breakable, which fractures when induced fractures are closed. U.S. Patent No. 4,741,401 (Walles, et al.) Discloses that a polymer can be applied to a solid fractionating chemical of More preferably through an air suspension coating. The Walles polymers are more typically homogenous and polyolefin copolymers and • ethylene oxides. This patent describes the release of the fractionator by rupture of the membrane, whether by the force of the closure of the fractures within the underground formation or by the osmotic pressure of the water diffusing into the envelope. In US Patent No. 5,164,099 (Gupta, • et al.), A polymer is applied to a solid particle of a fractionating chemical, by interfacial polymerization. Typically this polymer is a polyamide or a material cellulose reticulate. This patent discloses that the fractionator is released from the capsules described therein, by diffusion through the membrane of the encapsulation. U.S. Patent No. 5,591,700 (Harris, et al.) Refers to encapsulated fractionators that are coated with surfactants that are solid at ambient surface conditions and that dissolve at elevated temperatures in the formation underground. The surfactants are mixed from the dry state. The 2-cycloalkoxy alkyl monomers are polymerized immediately in the presence of a weak base, and as such have been widely used for the encapsulation and coating of particles in the pharmaceutical industry, primarily for the purpose of drug delivery. For example, Kante et al. (Int. J. Pharm., 1980,7,45) have described a method for preparing nanoparticles of actinomycin D using poly (butyl cyanoacrylate). U.S. Patent No. 4,452,861 (issued to RCA Corporation) discloses a method for coating fluorescent and phosphorescent, inorganic, luminescent substances using polymecyanoacrylates. The sketched procedure involves a five-step process and requires the complete evaporation of the non-aqueous solvent during each of the coating steps and a final step requiring the washing of the coated particles.

BRIEF DESCRIPTION OF THE INVENTION A paste composition is provided • Liquid of a viscosity fractionator, 5 encapsulated, to reduce the viscosity of a fracturing fluid. The fractionator is enclosed within a coating and is provided as a liquid paste together with a liquid that is selected such that the liquid paste global have a flash point above 93 ° C. The liquid is also selected such that it does not facilitate the release of the fractionator from the coating. The liquid paste also contains an auxiliary for The suspension in an amount sufficient to maintain the suspension of the encapsulated fractionator in the liquid. Methods of using these compositions in liquid paste of the fractionator are also provided of viscosity, encapsulated.

DETAILED DESCRIPTION OF THE INVENTION Although previously certain encapsulated viscosity fractionators have been used, a new format for the supply of encapsulated fractionators has been discovered, and the format provides surprising advantages over previous formats. It has been found that providing encapsulated fractionators, in a liquid paste format, has distinct advantages because these compositions are easy to transport, mix and pump, if they are compared. with the compositions of the prior art.

• Because the liquid paste composition preferably contains surfactant, the fracturing fluid will flow easily from the fractured formation after fractionation, and therefore provides easier cleaning of the underground formation. The liquid paste compositions of the present invention are easy to handle in •, the pumping site, because there is no need to use solids dosing devices. Therefore, time is saved at the work site because liquids mix faster, more completely and more easily, than solids with liquids. 25 Because the fractionator in a liquid paste composition can be mixed more easily and completely with the fracturing fluid, the fractionator will be distributed more • uniform in the fluid that is pumped into the perforation 5 and therefore will also be more effective in completing the fractionation of the fracturing fluid, even in the most remote parts of the underground formation. As an additional advantage, the format of liquid paste allows the user to simplify • To a large extent your logistics to maintain work artifacts. Because the materials can now be provided in a simple to use, stable, premixed format, the The number of components that must be ordered and maintained in inventory and / or that must be supplied to the drilling site, by the user, must be substantially reduced. In addition, it substantially reduces, as such, the probability of error on the part of the workers, on the site, when mixing the components in a wrong or inadequate way. Provide the encapsulated fractionator, in a liquid paste format, allows an optional surfactant to be present in an available liquid phase, at the time of mixing it with the fracturing fluid. This format helps to provide easy and complete mixing of the fractionator, through the fracturing fluid. Additionally, because the encapsulated fractionator is provided as a liquid paste to be mixed with the fracturing fluid, the material to be pumped into the perforation is more homogeneous in distribution, both of the fractionator and of the surfactant, in the composition . The use of the present invention can therefore result in less agglomeration problems, especially within the perforation, while removing the fracturing fluid, from the formation, because the fractionator is available throughout the fracturing fluid and the Surfactant is available at the fractionator site, to help remove the agglomerates that are in the fractionated fracturing fluid from the formation. The preferred fractionating material, for water-based fracturing fluids, may comprise, for example, enzymes such as hemicellulose, oxidants such as sodium or ammonium persulfate, acids or organic salts. • such as citric acid or a citrate, fumaric acid, liquids adsorbed on a solid substrate, solid perborates, solid peroxides or other oxidants, mixtures of two or more materials and the like. Most preferably, the fractionating material is potassium persulfate. 10 For hydrocarbon fracturing fluids, • gelled, the preferred fractionators include calcium oxide, calcium hydroxide, p-nor t robenzoic acid, triethanolamine, sodium acetate, sodium bicarbonate, and s imi lares. The coating of the encapsulated fractionator is any coating to protect the fractionator from the reaction • premature with the fractionating fluid and that at provides an appropriate release mechanism to allow the fractionator to reduce the viscosity of the fracturing fluid in the desired time frame, thereby allowing the removal of the formation material. underground. Examples of suitable coating materials include glass coatings, ceramic coatings, polyolefin homopolymers and copolymers and ethylene oxides, polyamides, cross-linked cellulose materials, polyureas, polyurethanes, dehydrated gums (such as guar), surfactant coatings. , and similar. The encapsulated fractionator of the present invention is preferably enclosed within a hydrolytically degradable polymer coating. By "hydrolytically degradable" it is meant that the polymeric coating will react with the water to chemically decompose the psi coating to predominantly non-solid components, at a time and temperature range appropriate for the intended use. Preferably the coating will be hydrolytically degraded in a time of four hours and at a temperature of 70 ° C. An encapsulated fractionator having a coating that degrades hydrolytically, is superior to prior art systems, because it allows better control of the release time and offers ease of handling not previously provided by the prior art systems. Because the fractionator is encapsulated in a material that reacts with water, instead of simply dissolving or dissipating in water, the release can be controlled by the rate of reaction of the coating with water. The fractionators are encapsulated of this type, preferred, are described in the application entitled ENCAPSULATED FRACTIONATORS, COMPOSITIONS AND METHODS OF USE (File No. 54239USA5A) filed on the same date this application was filed, "which is incorporated herein as The preferred polymeric shell material of the present invention is primarily a poly (2-cyanoacrylate alkyl), which is present in an amount sufficient to allow the coating to degrade hydrolytically at temperatures of use. above room temperature Preferably the poly (2-cyanoacrylate alkyl) is at least about 50% by weight of the total content of the coating, more preferably at least about 70% and most preferably at least about 90% • Other materials that can be incorporated into the coating of the material herein include comonomers that can be copolymerized with the alkyl 2-cyanoacrylate. The liquid of the liquid paste compositions, herein, is selected from • 10 such that the total liquid paste has a flash point above 93 ° C for safety considerations in transportation, measured in accordance with ASTM D 93-90 (standard analysis method for the point of inflammation through the use of a closed analysis device Pens y-Martens). In the case of solvents having flash points that are too low, the effective flash point of the liquid paste composition can be adjusted by mixing solvents. Therefore the liquid paste will be considered safe for transport from a perspective of ease of inflammation and ease of combustion. The liquid is further selected such that it does not facilitate the release of the fractionator from the coating. In this way, the liquid will not cause the diffusion of • fractionator out of the encapsulated envelope; the diffusion of the liquid to the capsule, thereby causing the break and release of the fractionator, prematurely; the dissolution of the encapsulation shell; the degradation of the envelope of encapsulated; or start any other mechanism # of release. Optionally the liquid of the liquid paste composition may comprise an oily or waxy material, to control additionally the time of liberation of the fractionator, in modalities wherein the liberation of the fractionator is effected by the contact of the coating with the water or other liquid. The access of water or other liquid to the The capsule wall, to initiate the release of the fractionator, can be retarded due to the coating of oil or wax. Optionally, the polymer coating the fractionating material can be chemically modified through the selection of the pendant functionality or surface treatment of the coated fractionator, such that the coated fractionator has an enhanced affinity for • Moisten an oily or waxy solvent. This additional affinity serves to provide additional short-term protection, coating, contact with water or other liquid. In this embodiment, a mixture of solvents is particularly contemplated, which a hydrophobic solvent will have a • affinity with the "coated fractionator, it can be provided in conjunction with a solvent that is more hydrophilic, the presence of the more hydrophilic solvent will serve to make that the liquid paste can be mixed more easily with an aqueous fracturing fluid. As a specific example, it has been surprisingly found that mineral oil is an extremely suitable liquid for use in liquid pastes of the encapsulated fractionator, for most of the coating materials. In this way, it has been found that polyurethane, polyurea coating materials, polyamides, pol i (2-cyanoacrylates of alkyl), and the like, are stable with respect to mineral oil. It has also been found that other liquids, such as hydrofluoroethers, are • liquids good for use in the formation of 5 stable liquid pastes of the present invention. Particularly preferred solvents are non-hygroscopic solvents that provide a liquid paste that can pumping, under the conditions of use. Examples • Preferred solvents include mineral oil (such as drilling mud oil), vegetable oil, canola oil, siloxanes, hydro fluoroethers and the like. The The materials are preferably selected so that the material can be pumped even at freezing temperatures. Additionally, solvents can be used • aliphatics such as alkanes or mixtures aliphatics that include kerosene. In the case of solvents having flash points too low, the effective flash point of the liquid paste composition can be adjusted by mixing solvents. Suspension aids, suitable for the use of the present invention, include surfactants and the like. Additionally they can be incorporated into pasta • liquid thickening agents. A preferred class of adjuvants for suspension are thickeners including natural extracts such as gum arabic, ghatti gum, khaya gum, agar, pectin, carrageenan and alginates; modified natural extracts; several rubbers which include guar gum, rhamsan gum, • xanthan gums; modified cellulose, such as sodium carboxymethyl cellulose, methyl cellulose and hydroxyalkyl celluloses; and synthetic polymers such as the carboxivini weight Ultra-high molecular weight (carbomers) and acrylic polymers; inorganic thixotropes such as fumed silica, tixo tropic clays, and titanates; polysaccharides (for example, • celluloses, starches, alginates); and similar. Preferably the liquid paste composition will maintain a uniform suspension at room temperature for at least two weeks. More preferably the liquid paste composition will maintain a uniform suspension to ambient temperature for at least one month.

The liquid paste composition of the fractionator preferably contains a surfactant. The surfactants • they provide an enhanced stability of the liquid paste and the uniform distribution of the particles suspended in the liquid paste, although the surfactant alone may not be sufficient to adequately suspend the encapsulated fractionator. The agents Preferred surfactants include the oxyalkylated phenolic resin surfactants, resin ester surfactants, polyol surfactants, alkylarylsulphonate surfactants, polymeric amine surfactants, ether alcohol sulfonates, cationic imidazoline surfactants, complex phosphate esters, alkylamine sulfonates, surfactants alkylamidoamine, polyamidoimidazole surfactants, fatty imidazoline surfactants, dimeric and trimeric acid surfactants, polyoxyethylated rosin amines, rosin amines Polyoxyethylated, polyoxyethylene glycol surfactants, ether alcohol sulphonate surfactants, ether alcohol sulfate surfactants, sulfonate surfactants, sodium alpha olefin surfactants, sodium ether alcohol sulphates, calcium alkylaryl sulphonates, Ibencenamine dodecyl sulfonates, fatty acid amides, alkanolamides, and mixtures thereof. These surfactants are generally known as surfactants for petroleum, and are generally commercially available from the Witco Company. Other surfactants include fluorinated surfactants, such as the 3M Fluorad ™ surfactants. Clays may be used in the liquid paste compositions of the present invention, including smectite clays including montmorillonites, hectorites and modified bentonites. To the liquid paste composition, support materials can additionally be provided to assist in keeping the fractured underground formation open, after rupture and elimination of the fracturing fluid. The support materials can be selected from any suitable material for the • introduction inside the hole, 5 including sand and sintered bauxite. The liquid paste composition containing the encapsulated fractionator may additionally comprise adjuvants suitable for incorporation into the compositions of the invention. fractionator, such as dyes, fragrances, • preservatives, anti-sedimentation agents, regulatory solutions for pH control, and viscosity modifiers. Typically the fracturing fluid is a Hydrated polymer such as guar, hydroxy alkyl guar, hydroxy to the cellulose, carboxyalkyl hydroxy, carboxyalkyl hydroxyalkyl, cellulose or other derivatized cellulose, Xantana and the like, in a aqueous fluid to which a suitable crosslinking agent is added. Suitable crosslinking agents include compounds such as borates, zirconates, titanates, pyroantimonates, aluminates and the like. The encapsulated fractionator of the present invention is preferably added to the fracturing fluid before the fluid is pumped into the perforation. In the preferred aspect of the present invention, the encapsulated fractionator is extremely stable even in the presence of water at ambient conditions above the ground, so that the mixture with the fracturing fluid can be carried out with due time and care, without worrying about premature decomposition of the the viscosity. Because the encapsulated fractionator is provided as a liquid paste, it can be easily mixed with the fracturing fluid without resorting to solids dosing devices. Most preferably, the liquid paste composition of the present invention is pumped simultaneously with the fracturing fluid, into the borehole, using liquid dosing devices. Optional equipment for mixing liquids can also be used in order to ensure uniform mixing of the two liquid streams.The following examples are provided for the purpose of illustrating the present invention, and are not intended to limit the broader concepts of the present invention. Unless stated otherwise, all parts and percentages are by weight.

Employ Example 1: A 1-liter polymerization flask equipped with stainless steel deflectors was charged with 300 milliliters of IPAR 3 drilling oil (commercially available from Petro-Canada) and 80 grams of industrial grade potassium persulfate. (60-100 mesh). For a period of about 20 minutes, 15 grams of ethyl 2-cyanoacrylate were added to the mixture. The persulfate salt was dispersed by stirring at 1500 RPM with a 6 blade turbine agitator. After stirring for approximately 10 minutes, 0.1 grams of triethanolamine was added to the suspension. Stirring was continued at room temperature for an additional 20 minutes in order to ensure a complete reaction of the cyanoacrylate. With continuous stirring, 17 grams of silicon dioxide "Cab-O-Sil M-5" was added to the mixture in order to provide a stable liquid paste of the coated persulfate particles.

Example 2: A 1-liter tripore vessel, equipped with stainless steel deflectors, was charged with 300 milliliters of hexanes and 80 grams of potassium persulfate industrial grade (60-100 mesh). The persulfate salt was dispersed by stirring at 1500 RPM with a 6 blade turbine agitator. Over a period of approximately 20 minutes, 15 grams of Loc-tite ™ 411 (85-90% ethyl cyanoacrylate, 10-15% poly (methyl methacrylate), 1-3% silica were added to the mixture. amorphous of vapors (free of crystals), 0.1% phthalic anhydride, 0.1-0.5% hydroquinone, lot number 7KP023A), and after stirring for approximately 10 minutes 0.1 grams of triethanolamine were added to the suspension. Stirring was continued at room temperature for an additional twenty minutes to ensure complete reaction of the cyanoacrylate. The white powder was collected by • filtration and redispersing in 350 5 milliliters of IPAR 3 drilling mud oil along with 3 grams of FluoradMR FC-760, fluorochemical surfactant (available in 3M) at a mixing speed of 1400 RPM. A pregel of clay, consisting of 120 milliliters of oil IPAR 3 drilling mud, 7.5 grams of Tixogel ™ clay MP150 and 3 grams of propylene carbonate and water, 95/5 mixed under high shear (Omni- Mixer, Omni International, Waterbury, Connecticut) for 20 minutes, were added to the pasta Liquid from the coated fractionator, and the mixture was stirred for an additional 30 minutes to ensure a stable and uniform suspension. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above it is claimed as property that contained in the following:

Claims (15)

RE IVIND ICAC IONE S

1. A liquid paste composition of an encapsulated viscosity fractionator characterized in that it comprises: a) a fractionator capable of reducing the viscosity of a fracturing fluid, enclosed within a coating, b) a liquid selected such that the liquid paste global have a flash point above 93 ° C, where the liquid does not facilitate the release of the fractionator, the coating, and c) an auxiliary for suspension, in an amount sufficient to maintain the suspension of the encapsulated fractionator, in the liquid.

2. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that it additionally comprises a support material.

3. The liquid paste composition of an encapsulated fractionator according to claim 1, characterized in that the auxiliary for the suspension comprises a surfactant.

4. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that the suspension aid comprises clay.

5. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that the coating is hydrolytically degradable.

6. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that the coating is made of poly (2-cyanoalkoxylate).

7. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that the coating is selected from the group consisting of glass coatings, ceramic coatings, homopolymers and polyolefin copolymers and ethylene oxides, polyamides, materials crosslinked cellulose, polyureas, polyurethanes, dehydrated gums and coatings of surfactants.

8. The liquid paste composition of the encapsulated fractionator according to claim 1, characterized in that the liquid is an organic solvent.

9. The liquid paste composition of the encapsulated fractionator according to claim 8, characterized in that the organic solvent is predominantly aliphatic.

10. The liquid paste composition according to claim 8, characterized in that the organic solvent is mineral oil.

11. The liquid paste composition, in accordance with the rei indication 8, characterized in that the organic solvent comprises a mixture of one or more hydrocarbons.

12. The liquid paste composition according to claim 3, characterized in that the surfactant is • selected from the group consisting of oxyalkylated phenolic resin surfactants, resin ester surfactants, polyol surfactants, alkylaryl sulphonate surfactants, polymeric amine surfactants, 10 alcohol ether sulfonates, agents • cationic imidazoline surfactants, complex phosphate esters, alkylarylamine sulfonates, alkylamidoamine surfactants, surfactants of Polyamidoimidazoline, surfactants of fatty imidazoline, dimeric and trimeric acid surfactants, polyoxyethylated rosin amines, polyoxyethylated rosin amines, surfactants of Polyoxyethylene glycol, alcohol ether sulphonate surfactants, ether alcohol sulfate surfactants, sulfonate surfactants, sodium alpha olefin surfactants, sulphates Sodium ether alcohol, calcium alkylaryl sulphonates, dodecylbenzenamine sulfonates, fatty acid amides, alkanolamides, fluorinated surfactants, and mixtures thereof.

13. A method for reducing or fractionating the viscosity of a fracturing fluid, characterized in that it comprises: a) mixing a liquid paste composition, encapsulated fractionator, according to claim 1, with a fracturing fluid, b) pumping the mixture into a formation underground and fracturing the formation; and c) allowing the fracturing fluid to fracture.

14. A method for reducing or fractionating the viscosity of a fracturing fluid, characterized in that it comprises: a) mixing a support material, at the site, with a liquid paste composition according to claim 1, b) mixing the composition formed in the step a) with a fractionating fluid c) pumping the composition formed in step b) into an underground formation and fracturing that formation, and d) allowing the fracturing fluid to fractionate.

15. A method for reducing or fractionating the viscosity of a fracturing fluid, characterized in that it comprises a) mixing the support material with a fractionating fluid b) mixing the composition formed in step a) with a "liquid paste composition, in accordance with claim 1, c) pump the composition formed in step b) into an underground formation and fracture that formation, and d) allow the fractionating fluid to fractionate.